Physics engine benchmark ideas.

Usually when doing performance testing on Chipmunk I just run time trials of whatever random demos I currently have in my demo application. For years I've thought that I really should make some proper benchmarking scenes, but have never really gotten around to it. Yesterday I finally started. So far I have these:

The idea here is mostly to test the speed of the solver and general collision detection algorithms. Objects quickly settle to their final places and don't move much afterwards.

1000 frictionless circles interacting with a complex static terrain (262 line segments):Similar to the first benchmark, but encouraging objects to move more. The balls fall into the basin and fill the tunnels.

500 perfectly elastic circles interacting with a complex, high resolution, static terrain (516 line segments):
Stress test the collision detection with moving objects. With no persistent contacts, the solver should take up very little of the CPU time.

28 moving circles moving through a grid of 825:
The moving circles bounce off the edges of the screen, but otherwise collisions never occur. More stress testing of the collision detection, but this time making sure that it's good at filtering out false positives.

Does anybody have other ideas of common physics usage that should be benchmarked? Also, anybody know what to use in place of gettimeofday() on Windows?.

It's plenty accurate, but gettimeofday isn't monotonic on the Mac since it is based on "wall clock" time, which can be updated/changed automatically, when you don't expect it to. I got slapped for this and use mach time now instead.
I just remembered ThemsAllTook posted his cross-platform time func not too long ago, here, which looks pretty good (in fact, that looks like where I got my Windows function I posted above).